Electrical precipitator with dual discharge electrodes



C. W. J. HEDBERG ELECTRICAL PRECIPITATOR WITH Sept. 11, 1951 DUALDISCHARGE ELECTRODES 3 Sheets-Sheet 1 Filed Aug. 18. 1948 c. w. J.HEDBERG 2,567,709 'ELECTRICAL PRECIPITATOR WITH DUAL DISCHARGEELECTRODES 3 Sheets-SheeiI 2 Sept. 11; 1951 Filed Aug. 18. v1948 HEDBERGELECTRICAL PRECIPITATOR WITH C. W. J.

DUAL DISCHARGEy ELECTRODES 3 Sheets-Shree?I :Ilm

l l w w Sept. l1, 1951 Filed Aug. 18, 1948 Patented Sept. 11, 1951ELECTRICAL PRECIPITATOR WITH DUAL DISCHARGE ELECTRODES Carl W. J.Hedberg, Bound Brook, N. J., assignor to Research Corporation, New York,N. Y., a

corporation of New York Application August 18, 1948, Serial No. 44,878

(Cl. 18S- 7) `6 Claims. 1

This invention relates to electrical precipitators and more particularlyto an electrical precipitator having at least two spaced sets ofdischarge electrodes and a single set of complementary extended surfaceelectrodes associated therewith. Although the invention is of generalapplication in the eld of electrical precipitation, it is especiallysuited to precipitators that operate under superatmospheric pressure athigh capacity to clean large volumes of gas bearing relatively highproportions of suspended matter.

An object of the invention is to provide an electrical precipitatorparticularly adapted to the cleaning of gases heavily loaded withsuspended particles of clay or the like such as petroleum vapors thathave been altered in composition by a catalytic cracking process inwhich a finely divided solid catalyst is suspended in the vapors. Suchprecipitators must withstand pressures of several pounds per squareinch, must be leak-proof, must be capable of collecting large amounts ofsuspended material, must run continuously, often for months without astop, and must efficiently clean the gases which pass through them.

Another object is to provide in a precipitator of this type supportmeans for the collecting and discharge electrodes enabling a highvoltage to be maintained between the electrodes for enhancing collectionefficiency.

Another object is to provide an electrical precipitator in which themajor components are vso varranged in a casing that space requirementsare reduced to a minimum.

Stillanother object is to provide an electrical precipitator in whichthe extended surface electrodes are readily cleaned without interruptingnormal operation of the precipitator.

The foregoing and other aims, objects and advantages of the invention asmay appear herein- In one illustrative embodiment of the inven-V tion,`the extended surface electrodes take the form of parallel pipes havingone set of discharge electrodes projecting into the pipes from one endof the assembly and another set of discharge electrodes projecting intothe pipes from the other end of the assembly. Cleaning of the pipeelectrodes is accomplished by flushing the surfaces thereof with awashing liquid that is introduced at one end of the pipes, flows throughboth precipitating zones and leaves the pipes at the other end of theassembly.

In another embodiment, the extended surface electrodes are of theparallel plate type. The plates may have internal conduits and openingsleading from the plate faces into the conduits for conduction of dustfrom thev exterior surfaces of the plates into the conduits and thencethrough the conduits to a dust hopper. This form of ,electricalprecipitator may include a verticalY cylindrical casing, baille means inthe casing defining an axially extending gas passage, the baille meanscooperating with the walls of the casing to define at least four`peripheral zones, diaphragm means extending between the bafile meansand the walls of the casing blocking flow of gas through the zones,complementary extended surface and discharge electrodes supported in theaxial gas passage, the support means for the discharge electrodesextending within at least two of the peripheral zones, gas inlet meansIcommunicating with at least two other of the peripheral zones on oneside of the diaphragm means, and gas outlet means on the other side Voi?the diaphragm means. v

The invention will be described with greater particularity withreference to the accompanying drawings in which:

Fig. 1 is a vertical sectional view of one form of precipitatorembodying the invention;

Fig. 2 is a fragmentary partly sectional view on an enlarged scale ofone of the discharge electrodes of the precipitator of Fig. 1;

Fig. 3 is a plan View of one of the discharge elements of theelectrodepf Fig. 2;

Fig. 4 is a vertical medial sectional view of another form ofprecipitator in accordance with the invention;

Fig. 5 is a vertical medial sectional view of the precipitator of Fig. 4taken fat `right angles thereto;

Fig. 6 is an elevational view of theprecipitator shown in Figs. 4 and 5;l

Fig. 7 is a plan view thereof with part lof the casing broken away toshow interior construction;

Fig. 8 is an enlarged fragmentary view of. a joint between a discharge`electrode and its supporting frame; and

vsimilar to the framework cipitated in two stages in the pipes I6.

Fig. 9 is an enlarged sectional View taken transversely of one of thecollecting electrodes of the second form of precipitator.

Referring to Figs. 1 through 3 of the drawings, the electricalprecipitator shown has a vertically extending casing including acylindrical central portionv Illand conical bottom and top portions I Iand I2 respectively. Positioned tranversely of the casing somewhat belowthe top thereof is a gas impervious plate or diaphragm member I3 that iscircular in horizontal extent and is welded or otherwise appropriatelysecured to the sidewalls of the cylindrical casing portion IB. The platemember I3 divides the casing into` an upper chamber I4 and a lowerchamber I5.

A plurality of parallel pipe sections I5 are supported in spaced holesformed in the plate I3, the tops of the pipe sections being flared at Ilto tightly engage the peripheries of the holes. Thepipe sections dependdeeply into the lower chamber I5. Each pipe section constitutes anAextended surface collecting electrode of the precipitator. l

The dual discharge electrode system includes an upper frame I8 supportedon insulators I9 and ID' mounted in the insulator housings 23 and 2I.The frame has parallel I-beams 22 extending horizontally over the rowsof pipe section I6 and the I-beams carry plates 23 that are pref- ;f

erably welded to the beams. From these plates, discharge electrodes 24project axially into each i of thepipe sections I6 and extend downwardlythereinto for somewhat more than half the length of the pipes.

Similar discharge electrodes 25 project axially upwardly into thebottoms of the pipe sections I6 and terminate .somewhat below the lowerends of electrodes 24. The lower assembly of electrodes 25 is carried bya framework 2S I8 described hereinbefore, the framework 26 being mountedon insulating supports 2l and 28 in housings 29 and 30.

The construction of the discharge electrodes 24 and 25 is shown ingreater detail in Figs. v2 and 3. The electrode has a central core inthe form of a rod 3|. A plurality of discs 32, each having a centralopening 33 and discharge points 34, are positioned on the rod 3| and arevspaced apart lengthwise of the rod by sleeves 34.

The composite electrode structure so assembled may be welded at theunsupported end 35 to form a unitary structure.

Gas to be cleaned is led into the precipitator through diametricallyopposed inlets 36 and 3l.

The gas flows down in the chamber I5 outside the pipes I3, reversesdirection near the bottom of the precipitator and flows upwardly throughthe pipes into the upper chamber I4 and passes out of the apparatusthrough the central outlet 38.

Suspended matter carried by the gas is pre- In operation the casing maybe grounded and the lower and upper sets of discharge electrodes may beseparately energized through the high tension cables 38 and 39 that arepassed through holes in the insulating bushings 21a and Illa and areconnected to the high tension frames 26 and I8, respectively. With thepresent arrangement, different types of energization may beapplied tothe spaced sets of discharge electrodes to secure optimum operatingconditions for the particular circumstances encountered.

The suspended material carried by the gas is precipitated upon the innerwalls of the pipes I6. Continuous or intermittent ushing of the walls ofthe pipes is employed to keep them in clean condition. For this purpose,a spray device including a header 40 having downwardly directed nozzles4I is positioned in the upper chamber I4 to discharge sprays of washingor ilushing liquid over the area of the tops of pipes I6. It will beseen that the diaphragm plate I3 and the walls of the casing I0 adjacentthereto provide a reservoir for the reception of flushing liquid whichrises in the reservoir to the level of the upper rims of pipes I6 andspills thereover to flow down the inner surfaces of the pipes and nushthem free from adherent precipitate.

The flushing liquid falls from the pipes I6 into the sump provided bythe lower casing section II and is withdrawn therefrom through theoutlet 42.

It will thus be seen that the collecting electrodes extend continuouslythrough both precipitating sections of the precipitator and providecontinuous paths along which precipitated material is conducted to thesump. Because of separate energization of the two serially arrangedprecipitating sections, most eicient precipitating conditions can bemaintained in each section.

Referring to Figs. 4 through 9 of the drawings, the form of precipitatorshown therein has a vertical casing including a conical bottom portion50, a cylindrical central portion 5I, and a conical top 52 havingrelatively gently sloping sides.

The collecting and discharge electrode assemblies are arranged centrallyof the cylindrical section of the casing to define a central verticalgas passageway having a substantially square horizontal cross-section,the corners of which passageway are contiguous with the walls of theshell and the sides of which form, in cooperation with the walls of treshell, four vertically extending peripheral zones having segmentalcross-sections. These segmental zones provide gas inlet and distributingchannels and compartments for electrode support members, as will appearmore fully hereinafter.

The collecting electrodes, generally designated by the reference numeral53, are preferably of the type sometimes referred to in the art as tulipelectrodes. The collecting electrode assembly includes a plurality ofvertically extending, horizontally spaced, parallel plate members 62that are hung from vertical members 60 which in turn depend fromhorizontal beams 54 supported by cantilever members 55 carried by thewalls of the shell. The outer collecting electrodes 53a have planesurfaces adjacent the inner walls of the shell portion 5I which form ineifect vertical baffles defining two of the four segmental zones 56 and5l. In order to simplify the drawings, some of the plate electrodes 53included between the outer plates 53a are shown as having planesurfaces, but it will be understood that such electrodes are of thetulip type to be described in greater detail hereinafter. Diaphragmplates 53 and 59 extend between the walls of the shell section 5I andthe collecting electrode support structure to seal 01T the tops of zones56 and 5l and thus to prevent flow of gas through these zones intochamber 52.

As shown in 9, the collecting electrode structure 53 has verticallyextending hanger rods SIJ, that are U-shaped in horizontalcross-section, t0 which are welded at vertically spaced intervals shell.

yhc'okfsupports 8|. The section of Fig. 9 is'taken through one of thehangers', a plurality of which are positioned in parallelfarrangement toform an open framework for theelectrode structure. Upon this framework,the outer plates 52, which extend horizontally across'each face of theelectrode, are secured by bending the top, outwardly flared edges of theplates as at -63 to engage the free ends of hooks 6| and securing thebottom edges 64 of the plates under the ngers 55 of .subjacent hooks 6|.The structure so formed presents a substantially plane vertical facehaving horizontal slots `66 extending thereacross.

The slots face upwardly to receive dust dislodged from the plates as byrapping and to direct the dust to the hollow interior of the electrodestructure and thence down through the interior to the inwardlyconverging lower portions 61 of the electrodes, and finally through thedust chutes 88 into the dust hopper :69 at the bottom of the Dust iswithdrawn from the hopper 69 through the outlet 1D as necessary. The'dust hopper is partitioned from the rest of the apparatus by a gratingof angle irons 1| supported by I-beams 12.

The collecting electrodes may be rapped periodically for the purpose ofloosening adherent dust and assisting its passage to the hopper 69.Rapper bars 13 extend through and are connected to the collectingelectrodes 53, asbest seen in Fig. 5. The ends of the bars are connectedto rappers 14 and transmit vibrations produced thereby'to the collectingelectrodes.

Gasto be cleaned is admitted to the precipitator through opposed gas`inlets 15 and carried downwardly in the zones 56 and 51 throughdownwardly flaring distributors 16 and is discharged .into the lowerportions of the zones.

The precipitator is provided with twovertical- 1y spaced sets ofdischarge electrodes arranged in complementary relation to thecollecting electrodes. As seen in Fig. 4, the lower set of dischargeelectrodes is carried `by va frame including upper cross members 11,vertical'hangers 18, and lower cross members 19. Longitudinal tie :rods19a join together the ends of the lower cross members'19 and providesubstantial bracing for :the lower discharge electrode assembly.Horizontal ydischarge elements B are carried by the hangers 18. Thedischarge elements have bulbous or rounded ends 8| facing outwardly tominimize undesired corona discharge therefrom.

As shown in detail'in Fig. 8, the dischargefelements 80 are formed oftwisted square rods providing helically disposed sharp discharge edges82. Thetwisted rods are retained in the hangers 18 by wedges 83 clinchedat 84 to hold them in place. Conveniently, horse-shoe nails are used aswedges.

Referring to Fig.v 4, it is seen kthat the lower.

discharge electrode structure is suspended by means of thesupportmembers 85 that are attached to the upper cross members 11 yof the frameand extend vertically upward through the segmental zones 86 and 81 thatare complemen tary to thezzones and 51 hereinbefore described. Zones 86and B1are defined between the vertical baies 88 and 99, thatsubstantially cover the open end area of the vassembly of collectingelectrodes 53,l and the adjacent side walls of the;-v

shell portion Segmental diaphragm plates 9i!V yand 9| are positionedacross the tops of the zones 86 and 81 and effectively seal off these'zones lagainst circulation of gas therethrough. The`yertical...separationof baffles 88 and 89 provides-ft!) DBrfOratedgaSdistributing Piate H iS horl- 6 openingsthrough which the frame members11 extend into the'segmental zones. 86 and 81.

Insulator housings 92 and 93 are positioned above the precipitator'shell.and are mountedion tubular Ysupports 94 that'pass through openings inthe casing top 52 and downwardly through trical cable passing through asuitable bushing in the housing 92 or 93 and connected to either of thebus bars 95, for example, and that the casing and collecting electrodeslare grounded `in a typical installation.

A rapping mechanism for the lower discharge electrode assembly includeselectrical vibrators 91 insulatedly supported over diametrically opposedsupport members 95. The support members are preferably tubular, andVibration 'transmitting rods 98 extend through the tubes 85 from thevibrators 91 to the horizontal frame members 11 for the purpose ofconducting vibrations therebetween. The -vibrators are operatedfromtimeto time toloosen dust that may accumulate on the lower dischargeelectrodeiassembly.

An upper discharge electrode assembly,1.gen

erally similar to the lower discharge electrode assembly hereinbeforedescribed, is mounted in complementary relationto theupper section ofthe collecting electrode assembly. The upper assembly includesthehorizontal frame members 99 vand |99 and the vertical frame members'|'0| that support the discharge electrodes |02 that are like thedischarge electrodes 89 'previously described. The rods |89a aresecuredto the outer ends of the lower horizontal frame members .|00 to bracethe discharge* electrode assembly. It will be seen that the tie rods |9aare positioned in the segmental zones 86 vand 81 whereample space isavailable to locate and apply these members easily and accurately.Support Amembers |03 suspend the assembly -fromvinsulated `supports inthe insulator compartments |84 and |05, as described hereinbefore`in-connection with .the lower electrode assembly. Rappers may beprovided in the insulator compartment extensions |06 for dislodging dustfrom the upper discharge electrode assembly. Separate energizing meanspreferably is provided for the upper discharge electrode assembly.

Dust collecting hoppers |91 Jarepositionedin the lower sections of thesegmentalzones 85 and 81 and have dust chutes |98 for conveying dustfrom the hoppers |01 tothecentral dust receiver 69. 'I'he hoppers V|91have upwardly facing mouths |09 substantially coextensive with thecross-sectional areas of `.the segmentalzones 86 and 81 and eiectivelyblock circulation of gas through the lower sectionsof these zones.

A central gas outlet ||9 is located -in the top section 52 of thecasing.

In operation, theelectrodes of `thepreci'pitator are energized fromconventional powerl sources (not shown) and gas burdened withparticulate suspended material is forced into the-gasinlet conduits 15.The gas flows downwardly through the flaring distributors 16 and issuesinto the lower portions vof segmental zones 59 Vand 51. A

zontally disposed across the casing below the precipitating zones. Byvirtue of the shape of the casing and the positioning of the baffles andgas distributing plate therein, the gas streams flow down through theperforated plate lll and converge towards the vertical axis of theprecipitator in the zone intermediate the plate l Il and the grating 1I.The gas streams merge with each other and are diverted upwardly to flowthrough the perforated plate Ill and through the central precipitatingzones in which they are substantially relieved of their burden ofsuspended material. The cleaned gases issue from the top of theprecipitator through the outlet conduit l I0.

The bulk of the precipitated dust accumulates on the collectingelectrodes 53. These electrodes are rapped as occasion demands by therappers 'H and the loosened dust falls through the slots 65 into theinterior of the collecting electrodes and passes down through theelectrodes and the dust chutes 68 into the receiver 69.

The discharge electrode structures may also be rapped from time to timeby the vibrators 91. Any dust that accumulates on the walls of thesegmental zones 86 and 8l, when loosened by action of the Vibrators orby incidental action, falls into the hoppers |01 and is conductedthrough the chutes |08 to the receiver t9.

From the foregoing description it will be seen that the presentinvention provides a precipitator that can be operated for long periodsof time at high efciency to clean gases under superat mospheric pressurecarrying heavy burdens of suspended matter. The construction includingplural precipitating zones. having collecting electrodes common to twoor morezones enables the collecting electrodes to provide continuouschane nels for the removal of dust from the commonly servedprecipitating zones.

In the form of the invention of Figs. 4 7, the arrangement of and themeans for mounting the plate electrodes in a cylindrical casing and theeffective utilization of space for gas distribution and for mounting thedischarge electrode assem blies contribute to the economical productionof an electrical precipitator for treating gases under superatmosphericpressure.

I claim:

l. An electrical precipitator comprising a vertical cylindrical casing,baille means in said casing defining an axially extending gas passage,said baille means cooperating with the walls of said casing to define atleast four peripheral zones, diaphragm means extending between saidbaille means and the walls of said casing blocking flow of gas throughsaid zones, extended surface collecting electrodes supported in saidaxial gas passage, an assembly of complementary discharge electrodesdisposed in spaced relation to said extended surface electrodes, supportmeans for said discharge electrodes extending within at least two ofsaid peripheral zones, gas inlet means communicating with at least twoother of said peripheral zones on one side of said diaphragm means, andgas outlet means on the other side of said diaphragm means.

2. An electrical precipitator as defined in claimv 1 including insulatorhousings positioned on the top of said casing and communicating withVthe peripheral zones in which the support means for said dischargeelectrodes extend, insulators in said housings, and means anchoring saidsupport means to said insulators.

3. An electrical precipitator comprising a ver- 8 I tical cylindricalcasing, baille means in said casing defining an axially extending gaspassage, said baffle means cooperating with the walls of said casing todene four peripheral zones, diaphragm means extending between saidbaille means and the walls of said casing blocking flow of gas throughsaid zones, horizontally spaced, vertically extending, parallel platecollecting electrodes supported in said gas passage, a set of dischargeelectrodes disposed in complementary relation to a lower section of saidcollecting electrode structure, support means for said set of dischargeelectrodes extending within two of said peripheral zones, a second setof discharge electrodes disposed in complementary relation to an uppersection of said collecting electrode structure, support means for saidsecond set of discharge electrodes, insulator housings positioned on thetop of said casing and communicating with said casing, insulators insaid housings, means anchoring said discharge electrode support means tosaid insulators, gas inlet means for supply of gas to the other two ofsaid peripheral zones below said diaphragm means, gas outlet means forconducting gas from said casing above said diaphragm means, and meansfor separately energizing said sets of discharge electrodes.

4. An electrical precipitator as dened in claim 3 wherein said parallelplate collecting electrodes have hollow interiors and are provided withupwardly facing parallel slots leading from the exterior to the interiorthereof and including a dust receiver and conduits conveying dust fromthe interiors of said collecting electrodes to said receiver.

5. An electrical precipitator comprising a casing, a lower precipitatingchamber including complementary precipitating and collecting electrodesmounted in said casing, an upper precipitating chamber includingcomplementary precipitating and collecting electrodes mounted in saidcasing above said first electrodes, means for passing gas to be cleanedthrough said precipitating chambers, means for energizing saidelectrodes, a receiver mounted below said lower precipitating chamberand communicating with said lower precipitating chamber for the passageof precipitated material from said lower chamber to said receiver, andmeans including substantially enclosed conduit means for conductingprecipitated material from said upper precipitating chamber through saidlower precipitating chamber to said receiver in a stream substantiallyshielded from the ilow of gas and the electric field in said lowerprecipitating chamber.

6. An electrical precipitator comprising a vertical casing, baffle meansin said casing dening an axially extending gas passage, said baillemeans cooperating with the walls of said casing to dene at least twoperipheral zones, diaphragm means extending between said baille meansand the walls of said casing blocking flow of gas through said zones,vertically extending extended surface collecting electrodes supported insaid axial gas passage, a set of complementary precipitating electrodesmounted in precipitating relation to the upper portions of saidcollecting electrodes, insulated supports in said peripheral zones, asecond set of complementary precipitating electrodes carried by saidsupports and mounted in precipitating relation to the lower portions ofsaid collecting electrodes, gas inlet means communicating with at leastone of said peripheral zones on one side of said diaphragm 1U means, gasoutlet means on the other side of said REFERENCES CITED diaphragm means'means for energlzmg said The following references are of record in theelectrodes, a receiver formed in the lower portionbf said casing belowsaid electrodes', and me of this patent' conduit means for conductingprecipitated ma- UNITED STATES PATENTS terial from the upper portions ofsaid collecting 5 Number Name, Date electrodes to said receiver throughthe lower por- 1,440,887 Nesbit Jan. 2, 1923 tion of said axiallyextending gas passage in a 1,992,113 Anderson 1 Feb. 19, 1935 streamsubstantially isolated from the now of g'as and the electric field inthe lower portion of FOREIGN PATENTS said axially extending gas passage.lo Number Country Date 728,209 France t Apr. 11, 1932 CARL W, J.HEDBERG, 219,570 Great Britain July 31, 1924

